1. Field of the Invention
The present invention relates to the field of telecommunications. More particularly, the present invention relates to cellular or Personal Communications Services (PCS) network systems, and mobile stations having intelligent roaming and over-the-air programming features.
2. Acronyms
The written description provided herein contains acronyms which refer to, for example, various telecommunication services, components and techniques, as well as features relating to the present invention. Although some of these acronyms are known, use of these acronyms is not strictly standardized in the art. For purposes of the written description herein, acronyms will be defined as follows:
Advanced Mobile Phone Service (AMPS) PA1 Analog Control Channel (ACC) PA1 Base Station/Mobile Switching Center/Interworking Function (BMI) PA1 Code Division Multiple Access (CDMA) PA1 Complimentary Metal Oxide Semiconductor (CMOS) PA1 Control Channel (CCh) PA1 Customer Service Center (CSC) PA1 Digital Control Channel (DCCH) PA1 Digital Traffic Channel (DTC) PA1 Electronically Erasable Programmable Read Only Memory (EEPROM) PA1 Federal Communications Commission (FCC) PA1 Group System for Mobile Communications (GSM) PA1 Home Location Register (HLR) PA1 International Mobile Station Identity (IMSI) PA1 Intelligent Roaming Mode (IR Mode) PA1 Interim Standard (IS) PA1 Liquid Crystal Display (LCD) PA1 Mobile Identification Number (MIN) PA1 Mobile Station (MS) PA1 Mobile Switching Center (MSC) PA1 Mobile Telephone Switching Office (MTSO) PA1 Number Assignment Module (NAM) PA1 Over-the-Air Activation Function (OTAF) PA1 Over-the-Air Activation Teleservice (OATS) PA1 Personal Access Communication System (PACS) PA1 Personal Communications Network (PCN) PA1 Personal Communications Services (PCS) PA1 Public Land Mobile Network (PLMN) PA1 Public Switched Telephone Network (PSTN) PA1 Random Access Memory (RAM) PA1 System Access List (SAL) PA1 System Identification Code (SID) PA1 System Operator Code (SOC) PA1 Transmission Control Protocol/Internet Protocol (TCP/IP) PA1 Time Division Multiple Access (TDMA)
3. Background and Material Information
The use of wireless or mobile communication devices has increased greatly in recent years. Mobile and cellular telephones have enabled mobile station users to roam over large geographic areas while maintaining immediate access to telephony services. Mobile stations include portable units, units installed in vehicles and fixed subscriber stations. Mobile stations comprising cellular telephones or wireless handsets are operable in cooperation with cellular or Personal Communications Services (PCS) communications systems. Cellular communication systems typically provide service to a geographic area by dividing the area into many smaller areas or cells. Each cell is serviced by a radio transceiver (i.e., a transmitter-receiver base station or cell site). The cell sites or base stations may be connected to Mobile Telephone Switching Offices (MTSOs) or Mobile Switching Centers (MSCS) through landlines or other communication links, and the MTSOs may, in turn, be connected via landlines to the Public Switched Telephone Network (PSTN).
FIG. 1 illustrates the basic components of a conventional cellular network. As shown in FIG. 1, a mobile station 38 may place or receive calls by communicating with a cell site 30 or a cell site 40, depending upon the geographic location of the mobile station and the cell coverage area that is provided by each cell site (i.e., cell coverage area 35 of cell site 30 or cell coverage area 45 of cell site 40). For purposes of illustration, mobile station 38 is depicted in FIG. 1 as being able to communicate with either cell site 30 or cell site 40, even though the mobile station is not illustrated as being located within cell coverage area 35 or cell coverage area 45. Under normal operating conditions, the extent to which mobile station 38 will be able to communicate with cell site 30 or cell site 40 will depend on the geographic location of the mobile station and the size of the cell coverage area of each cell site. Further, although only two cell sites are depicted in FIG. 1, the entire cellular network may include, for example, more than two cell sites. In addition, more than one cell site may be connected to each MTSO.
Mobile station 38 may include a conventional cellular telephone unit with a transceiver and antenna (not shown) to communicate by, for example, radio waves with cell sites 30 and 40. Various air-interface technologies may be implemented to facilitate communication between the mobile station and the cell sites. Cell sites 30 and 40 may both include a radio transceiver (not shown) and be connected by landlines 16 or other communication links to MTSOs 24 and 28. The PSTN 12 is also connected to each MTSO 24 and 28 by landline 16 or other communication links.
The MTSOs 24 and 28 may be conventional digital telephone exchanges that control the switching between PSTN 12 and the cell sites 30 and 40 to provide wireline-to-mobile, mobile-to-wireline and mobile-to-mobile call connectivity. The MTSOs 24 and 28 may also (i) process mobile station status data received from the cell site controllers; (ii) handle and switch calls between cells; (iii) process diagnostic information; and (iv) compile billing information. The transceiver (not shown) of each cell site 30 and 40 provides communications, such as voice and data, with mobile station 38 while it is present in its geographic domain. The MTSOs 24 and 28 may track and switch mobile station 38 from cell site to cell site, as the mobile station passes through various coverage areas. When mobile station 38 passes from one cell to another cell, the MTSO of the corresponding cell may perform a "hand-off" that allows the mobile station to be continuously serviced.
In the current North American cellular system, any given area may be serviced by up to two competing service providers of cellular air time communication services. By Federal Communications Commission (FCC) regulations, the two competing service providers are assigned different groups of frequencies through which services are provided. A frequency set typically includes control channels and voice channels. The control channels are used for preliminary communications between a mobile station and a cell site for setting up a call, after which a voice channel is assigned for the mobile station's use on that call. The assigned frequency sets are generally referred to as "A band frequencies" and "B band frequencies". Typically, the A band frequencies are reserved for non-wireline service providers, while the B band frequencies are reserved for wireline service providers. While each frequency set for a given cellular service area is assigned to only one service provider, in different service areas the same frequency set may be assigned to different service providers or companies.
Depending upon which service provider is subscribed to by the user of the mobile station, the home frequency set of the user may correspond to the A frequency band or the B frequency band. Whenever a call is placed by the mobile station, the unit will ordinarily attempt to use the home frequency set to establish the call. If a call is handled outside of the user's home network area, then the unit is said to be "roaming" and service will be attempted through a frequency set of a non-home service provider. Typically, the user's home service provider will have a roaming agreement or -reciprocal billing arrangement with the non-home service provider to permit service to be extended to the user's mobile unit when it is roaming in the non-home service provider's service area.
The mobile station may include a memory device, such as a number assignment module (NAM), in which an assigned phone number and a system identification code (SID) is stored to uniquely identify the home service provider for the unit. In the North American cellular system, each cellular market or provider is assigned a distinct, fifteen bit SID. In Europe, on the other hand, the Global System for Mobile Communications (GSM) standard (see, for example, Recommendation GSM 02.11, Service Accessibility, European Telecommunications Standards Institute, 1992) defines a process for network selection based on the mobile station reading the GSM equivalent of the SID, called the Public Land Mobile Network (PLMN) identity. The SID or equivalent system identification number is broadcast by each service provider or cellular provider and is used by the mobile station to determine whether or not the mobile station is operating in it's home network or if it is operating in a roaming condition. The mobile station makes this determination by reading the SID that is broadcasted in the cellular market in which it is located, and comparing it to the home SID stored in the NAM of the cellular phone unit. If the SIDs do not match, then the mobile station is roaming, and the mobile station must attempt to gain service through a non-home service provider. Due to the imposition of a fixed surcharge or higher per unit rate, the air time charges when the mobile station is roaming are customarily higher than when it is operating within its home network.
Operation under a roaming condition is often under the control of the mobile station user. The user can select whether the mobile station will operate in a Home System Only, A Band Only, B Band Only, A Band Preferred, or B Band Preferred operating mode. The user typically controls the system preference and mode operation through menu choice or selection. This current method of roaming control is conventionally known as "Preferred System Selection". In the most common roaming situation, the mobile station remains on the same band as the home cellular network. That is, if the mobile station is homed to a cellular network with an odd numbered SID (which is normally assigned to an A band cellular service provider), then the mobile station will obtain service from the A band cellular service provider when roaming.
Occasionally, the home service provider will program a mobile station with negative SIDs. Negative SIDs correspond to SIDs on which the mobile station should not obtain service. Negative SIDs may be used, for example, if roaming agreements are not in place between different cellular service providers. An example of a mobile station that utilizes negative SIDs is disclosed in BLAIR, U.S. Pat. No. 4,916,728. As an alternative to negative SIDs, some mobile stations are programmed with positive or preferred SIDs. Positive or preferred SIDs are SIDs on which the mobile station should attempt to obtain service when selecting a cellular carrier frequency. An example of a mobile station that utilizes preferred SIDs is disclosed in BARBER et al., U.S. Pat. No. 5,442,806. The use of preferred SIDs facilitate the selection of a preferred service provider when the mobile station is roaming.
Presently, there is a need in the cellular and mobile network industries to provide some form of "intelligent" or "automatic" roaming in which the mobile station obtains service on the cellular network with which the home cellular service provider has the best roaming agreement (or the cellular service provider's own network in the roaming area, if it is not in the same band as the home system). There are three factors that have primarily led to this need. First, large cellular service providers rarely operate in the same band in all markets. Secondly, cellular service providers have chosen to implement three distinct technologies at 800 MHz (i.e., Analog Only, Time Division Multiple Access (TDMA), and Code Division Multiple Access (CDMA)), and the mobile station may have to change bands to obtain service on the preferred technology. Third, with the advent and development of Personal Communications Services (PCS), there is an increasing desire for roaming to, for example, 1900 MHz PCS systems.
As will be appreciated by those skilled in the art, PCS covers a broad range of individualized telecommunication services that let users communicate irrespective of where they are located. With PCS, personalized numbers are assigned to individuals rather than to the mobile stations, and call completion is performed regardless of the location of the user. PCS may be implemented through conventional macrocellular techniques or through Personal Communications Networks (PCN) that utilize light, inexpensive handheld handsets and communicate via low-power antennas that are intended to operate in a similar fashion to that of large scale cellular telephone networks, but operate within small geographic or microcellular areas. It is anticipated that PCNs will operate within the same frequency band in most countries (e.g., 1850-1990 Mhz), while cellular systems will operate in different frequency bands in various countries.
In the marketplace today, there is also a need to provide intelligent roaming capabilities in order to reduce scanning and acquisition time, and to permit a mobile station to more quickly determine which system it should obtain service on prior to registration. In conventional systems, including systems that utilize negative or preferred SIDs, the mobile station will typically scan a plurality or all of the available frequency bands before determining the preferred carrier for a present service locality. It would be desirable to provide intelligent roaming capabilities for a mobile station to reduce the time and amount of scanning that is required by the mobile station when seeking a non-home network service provider. Prior systems do not provide, for example, sufficient intelligence in the mobile station to efficiently direct the mobile station to the particular band or bands where the mobile station may obtain service on a preferred system when it is roaming.
Further, there is a need to provide intelligent roaming capabilities for a mobile station which will not require any changes to present network interface standards (e.g. IS-41) or air interface standards (e.g., IS-136, IS-91A, IS-95), and which is independent of air interface technologies (e.g., Advanced Mobile Phone Service (AMPS), TDMA, CDMA, Personal Access Communication System (PACS) and PCS-1900 MHz). Such features are desirable in order to permit new intelligent roaming capabilities to be readily utilized by a mobile station and to allow seamless integration of such capabilities without modification to present industry standards. For more information on network interface standards such as Interim Standard 41 (IS-41), see, for example, TIA/EIA-IS-41.5-C, Cellular Radiotelecommunications Intersystem Operations: Signaling Protocols, Telecommunications Industry Association, February 1996. For more information on air-interface standards such as Interim Standards 95 and 136 (IS-95 and IS-136), see, for example, TIA/EIA-IS-95-A, Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular Systems, Telecommunications Industry Association, May 1995; TIA/EIA-IS-136.1-A, TDMA Cellular/PCS-Radio Interface-Mobile Station-Base Station Compatibility-Digital Control Channel, Telecommunications Industry Association, October 1996; TIA/EIA-IS-136.2-A, TDMA Cellular/PCS-Radio Interface-Mobile Station-Base Station Compatibility-Traffic Channels and FSK Control Channel, Telecommunications Industry Association, October 1996; and TIA/EIA/IS-136.1-A-1, Addendum No. 1 to TIA/EIA/IS-136.1-A, Telecommunications Industry Association, November 1996.
Another desirable feature is to provide over-the-air programming of a mobile station to permit reprogramming of the mobile station with new intelligent roaming information as it becomes available. Such a feature would permit the "intelligence" that is incorporated into the mobile station to be updated and stored with ease, without requiring the user to bring the mobile station to a technician or operator for reprogramming.